Note: Descriptions are shown in the official language in which they were submitted.
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PARKING BRAKE INVALIF'F INTERLOCK SYSTEM
BACKGROUND
[0001, This invention relates to a system for a vehicle with an invalid or
wheelchair lift. The
system provides an interlock with the vehicle parking brake system and vehicle
ignition that
prevents a driver of the vehicle from moving the vehicle in any gear unless
the invalid lift is stowed,
the lift door is closed, and the parking brake released. There are regulations
that provide some
guidance on the controls of a vehicle invalid lift. The regulations indicate
that the lift controls
should be interlocked with the vehicle brakes, transmission, or door, or shall
provide other
appropriate mechanisms to ensure that the vehicle cannot be moved when the
lift is not stowed
and the lift cannot be deployed unless the interlocks or systems are engaged.
The regulatory
guidance does not provide any specifications as how to accomplish this
interlock. Many vehicles
that may contain invalid lifts, such as school buses, use parking brake
systems that use air to keep
the parking brakes engaged. Should the air pressure in the system be reduced,
the parking brake
actuators are engaged to the release of stored energy in the actuators. If air
is bled out,of the
parking brake actuators or chambers, the actuators engage the park brake and
the vehicle may not
be moved in any gear. No previous invalid lift system tied the vehicle
movement interlock to a
reduced air or other actuating fluid pressure to the parking brake actuator.
[0002] What is needed is a practical system that locks out vehicle movement of
any kind
through the air or other fluid pressure sensed position of the park brake and
further prevents the
release of the park brake until the lift is stowed, the lift door is closed,
and vehicle ignition is turned
on.
SI~MMARY
[0003, An objective of the invention is to provide a vehicle system and a
vehicle with the
system installed where the vehicle parking brake must be set before an onboard
vehicle lift can be
operated. More specifically, the objective is that the lift cannot be operated
unless the vehicle
ignition is energized, there is power to the lift, the park brake operating
fluid system is
depressurized engaging the park brake, and the lift door is opened. A further
objective is to
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provide that the parking brake cannot be released and the vehicle cannot be
moved in any gear
until the lift is stowed, the lift door is closed, and the ignition is turned
on.
[0004] The parking brake invalift interlock system of this invention meets the
objectives of the
invention. Specifically, the system includes electrical communication with a
park brake valve. This
valve in a closed position will prevent air or other actuating fluid from
releasing the park brakes.
The park brake valve is engaged to the circuit of the interlock system such
that the valve cannot be
opened to release the park brake unless the vehicle ignition is in an ON or
energized position, the
lift is stowed, and the lift door is closed. The invalid or wheelchair lift,
referred to as an invalift, is
electrically engaged through the interlock system to the ignition system, a
park brake pressure
sensor, and a lift door position sensor. As a result, the i~vaiift lift
control cannot be operated unless
the ignition is ON, there is power to a Lift Switch, the park brake system
fluid or air pressure is
below a predefined pressure set point, and the lift door is opened. The system
may further be
configured to prevent lift door opening unless the ignition is in the ON
position. This would be to
ensure that the lift has the power to operate.
DRAWINGS
j0005] Other objects and advantages of the invention will become more apparent
upon
perusal of the detailed description thereof and upon inspection of the
drawings, in which:
(0006] Figure 1 is a perspective view of a mobile bus vehicle with an invalift
and parking
brake invalift interlock system installed made in accordance with this
invention.
j0001] Figure 2 is a top down partial view of the chassis of the vehicle of
Figure 1.
(0008] Figure 3 is a logic diagram of an invalift control portion of the
interlock system of Figure
1.
[0009] Figure 4 is a logic diagram of a parking brake portion of the interlock
system of Figure
1.
[0010] Figure 5 a logic diagram of an invalift lift door portion of the
interlock system of Figure
1.
[0011] Figure 6 is one embodiment of a circuit for the parking brake invalift
interlock system of
Figure 1.
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[0012] Figure 7 is a second embodiment for implementing the parking brake
invalift interlock
system of Figure 1.
[0013] Figure 8 is an additional embodiment of a circuit for the parking brake
invalift interlock
system of Figure 1.
~ETAILS ~F INVENTION
[0014] The parking brake invalift interlock system of this invention is well
suited for use in a
mobile vehicle 101, such as a school bus, commercial bus, or light duty
vehicle like a transit van. A
school bus vehicle 101 with the system installed is shown in Figunrs 1 and 2.
The vehicle 101 has
a chassis 102 comprised of two generally parallel frame rails 103, with
interconnecting cross
members 104. There is a forward axle assembly 105 and a rear axle 106 engaged
to the frame
rails 103 through a suspension system. The forward axle assembly 905 has front
wheels 108,
while the rear axle 106 has rear wheels 109. Each of the wheels 108 and 109
has a brake
assembly 110. Each brake assembly 110 has an associate brake actuator chamber
112. Each
associated brake actuator chamber 112 will engage the park brakes on the
associated brake
assembly 110 when air or other actuating fluid is bled from the actuator
chamber 112. A spring or
other potential energy storing device is held in a disengaged position due to
the presence of
pressurized air or other actuating fluid. The air or other actuating fluid is
plumbed from an
actuating fluid source 116 through park brake valve 115 to the actuating
chambers 112 through
tubing or piping 114. Where the actuating fluid is air as in air brakes the
fluid source 116 will be a
vehicle air tank 116 or air compressor. The park brake valve 115 may be
operated in a number
ways although a solenoid 115a is described here. Should air brake valve 115 be
operated by
another means such as hydraulic or air, that source's control would be
regulated in a similar
fashion as solenoid 115a is described here. In an alternative embodiment, the
parking brake
system may involve. locking a drive shaft engaged to the rear axle 106. The
shaft parking brakes,
there would be a brake actuator chamber 112 that would engage the drive shaft
to lock the shaft.
The remainder of the interlock logic to be described here would be the same.
[0015] The vehicle 101 will have a body 118 engaged to the chassis 102. The
body 118
contains a driver control area 105 and a passenger area. The vehicle ignition
151 is within the
driver control area 105. The ignition system 151 provides electrical power to
the interlock system
in the hard wire embodiment of Figure 6. The .driver control area 105 contains
the controls for
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operating the parking brake system. l~he body 118 has a lift door access area
119. A lift door 120
is used to close off the lift door access area 119 when an invalid or
wheelchair lift 121, also
referred to here as an invalift 121, is not in use. The invalift 121 operates
through the access area
119. Invalifts 121 in general may operate in various methods. The specific
invalift described here
is not critical to the invention. The interlock system need only be able to
sense the specific invalift
parameters and control status in order to achieve the interlock functionality.
Similar parameters
and control would be available for any invalift. The invalift 121 shown has an
operating control
122. The operating control 122 functionality may be achieved through
electrical or hydraulic power
or some combination. The invaiift will have a movement platform 124 for
allowing an invalid or
wheelchair 191 to be moved onto or off of the vehicle , body 118. The movement
platform 124
shown is lowered along extending struts 123 which retract into the body 118
through the access
area 119 when the invalift 121 is not in use. There may be lift stowed sensor
125 along to detect
the invalift 121 in a stowed position. There may be a lift door sensor 126 for
sensing the position of
the lift door 120. The most important indication being if the lift door 120 is
closed. In the invalift
121 shown, the lift door 120 cannot be closed unless the invalift 121 is in a
stowed portion. In that
embodiment, the lift stowed sensor 125 is not necessary because an indication
of lift door 120
closed from the lift door sensor 126 is also an indication that the invalift
121 is stowed.
[0016] The parking brake invalift interlock system functionality options are
shown in Figures 3,
4, and 5. The logic diagram of an invalift control portian of the interlock
system is shown in Figures
3. This is the logic that prevents the operation of the invalift 121 unless a
series of conditions exist.
For the invalift lift control 152 to be operated, the ignition 151 must be in
the ON or energized
position. This ignition 151 position also will start the vehicle engine or
allow continued operation of
the engine or accessories. Additionally, a lift power switch 153 must be ON.
Additionally, the park
brake system pressure switch 117 must be below a predetermined set point. The
predetermined
set point is set such that the brake actuator chambers) 112 apply the parking
brakes. Lastly, the
lift door 120 must be opened. If these conditions are met, the series logic
will allow a lift control
952 to be operated.
[0017] The logic diagram of a parking brake portion of the interlock system is
shown in Figure
4. This is the logic that prevents a driver of the vehicle 101 from moving the
vehicle 101 unless a
series of conditions exist. For the park brake to be released to allow vehicle
101 movements, the
park brake solenoid 115a must be operated to open the park brake valve 115.
For the park brake
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valve 115a to be operated; the ignition 151 must be ON. Additionally, the
invalift 121 must be
stowed and the lift door 120 must be closed. The door position sensor 126
would provide this
indication and hence allow the series logic to be a complete circuit. As
mentioned in the
embodiment shown, the lift door 120 may not be closed until the invalift 121
is in a stowed position.
If the above conditions are met, the park brake solenoid 115a may be operated
to open the park
brake valve 115 to allow air or operating fluid to overcome potential energy
of the brake chambers
or actuators 112 to release the park brake.
[0018j An additionally option may be to prevent lift door 120 opening unless
one condition is
met. The logic diagram of an invalift lift door portion of the interlock
system is shown in Figure 5.
The ignition 151 must be ON.
[0019] The various parking brake invalift interlock system functionality can
be installed in a
vehicle 101 through hard wiring such as shown in the preferred embodiment of
Figure 6, the
alternative embodiment of Figure 8, or the interlock system may be the
programming of an
electronic control unit that is in communication with the sensors and valves
and controls such as
shown in Figure 7.
(0020] The hard-wired embodiment of Figure 6 includes the functionality of
Figures 3, 4, and
although some combinafion that does not include all three may be made. The
invalift portion of
the functionality of Figure 3 is shown in the Figure 8 wiring from the
ignition 151 through the lift
power switch 153 to a lift enable relay 154. The lift power switch 153 must be
closed indicating
that there is power to the invalift 121. The lift enable relay 154 will not
close to allow ignition power
through unless there is closure across contacts 30 to 87. These contacts are
not closed across
unless a lift door switch 155 is closed by the operation of a lift door 120
control in the driver area
105. The park brake pressure switch 117 must be closed indicating the sensed
reduced air or
operating fluid pressure in the park brake system. The preferred air
embodiment set point will be
an air depressurization to between 2 and 6 psig although the pressure must be
that which results in
the engagement of the park brake. A lift master solenoid 152 acts as the lift
control 122 in the
embodiment shown. The lift master solenoid cannot be operated unless there is
current through
the ignition 151, the lift switch 153, the lift enable relay 154 as a result
of lift door 120 operation
through lift door switch 155, and the park brake switch 117. The series make-
up across the sub-
circuit of Figure 6 hence embodies the series logic of Figure 3.
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(0021] The parking brake enable portion of Figure 4 is shown in the Figure 6
hard-wire
embodiment as follows. The ignition 151 must he ON to provide power through a
closed lift door
126 sensor. This lift door sensor 126 will be closed when the invalift 121 is
stowed and the lift door
120 is closed as described above. This will allow appropriate power through
.the park brake
solenoid 115a allowing release of the park brakes of the vehicle 101.
(0022] The lift door interlock portion of Figure 5 is shown in the Figure 6
harc!-wire
embodiment in that the ignition switch 151 must be ON along with the door
switch 155 to open to
allow operation of a lift door control 128.
(0023] The simplest embodiment of this invention would have the park brake
pressure switch
117 in series as the sole condition for allowing operation of the invalift
121. Closure of the park
brake pressure switch would allow power to flow.through a lift control switch
152 from a lift control
power supply 353. This simplest embodiment might be somewhat more complex by
containing a
simple circuit with the door position sensor 926 indicating a closed position
providing the sole
condition for allowing the park brake solenoid 115a from repositioning the
park brake valve 115
from opening and allowing disengagement of the park brake. This simplified
embodiment is shown
in Figure 8. There would be a power source 351 or 351 a for each logic sub-
circuit. These power
sources 351 and 351 a may be but nat necessarily are the same source. The
fluid of source 116
need operate only one actuating chamber 192. This could be for operation on a
wheel or a drive
train component.
(0024] In a programmed controller version of the invention, shown in Figure 7,
a vehicle
electronic control unit (ECU) 201 is engaged to communicate with a common data
link 219 of the
vehicle 101. Communication along the data link 219 can be by a multiplexed
automotive industry
standard such as Society of Automotive Engineers (SAE) ]9939 or by a
proprietary protocol.
There is a door communication controller 220 for the lift door 120; the door
communication
controller 220 is also engaged to the common data link 219. Lift door switch
position may be
separately communicated to the common data link through a door position sensor
126 or it may be
included within the door communication controller 220. The park brake solenoid
or other actuator
115a or the park brake valve 115 may also be engaged to the common data link
219. The ECU
201 may control or have input to park brake valve 115 operation and hence
release of the park
brake. The park brake pressure switch 117 is also engaged to communicate its
status along the
common data link 219. The ignition 151 and the invalift lift control 122 are
also engaged to
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communicate on the data link. The logic of Figures 3, 4, and 5 may be
programmed into the ECU
201. The ECU 201 directs and controls the logic through communication and
control signals along
the common data link 219. The ECU 201 may be a main vehicle ECU for
controlling a number of
other vehicle components such as engine, transmission, and anti-lock brake
controllers. The
simplified logic of the embodiment of Figure 8 may also be programmed into a
multiplexed ECU
201.
[0025, As described above, the parking brake invalift interlock system and the
vehicle 101 with
the interlock system installed provide a number of advantages, some of which
have been described
above and others of which are inherent in the invention. Also modifications
may be proposed to the
parking brake invalift interlock system and the vehicle 101 with the interlock
system installed
without departing from the teachings herein.
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